f90wrap is a tool to automatically generate Python extension modules which interface to Fortran libraries that makes use of derived types. It builds on the capabilities of the popular f2py utility by generating a simpler Fortran 90 interface to the original Fortran code which is then suitable for wrapping with f2py, together with a higher-level Pythonic wrapper that makes the existance of an additional layer transparent to the final user. f90wrap has been used to wrap a number of large software packages of relevance to the condensed matter physics community, including the QUIP molecular dynamics code and the CASTEP density functional theory code.

Low-cost spray deposition is employed to investigate the suitability of spray-deposited Al₂O₃ for rear passivation and optical trapping in passivated emitter rear contact (PERC) Si solar cells. Structural, optical, and electrical properties of spray-deposited Al₂O₃ films are investigated. Capacitance-voltage measurements indicate that spray-deposited Al₂O₃ has a negative charge density of 3.19 X 10¹²cm^-2 for an 80-nm film, suggesting that it can serve as the passivation layer. Optical properties of spray-deposited Al₂O₃ are identical to the Al₂O₃/SiN_x stack prepared by atomic layer deposition and plasma-enhanced chemical vapor deposition, indicating that it can also serve as the optical trapping layer. Atomic force microscopy studies show that spray-deposited Al₂O₃ is crack and pore free, and its surface roughness has a root-mean-square value of 0.52 nm for an 80-nm film.

Single-electron transistor (SET) device fabrication for operation in the tens of Kelvin range is still challenging due to the need of controlled definition of the metallic island with a diameter far below 100 nm and proper tuning of the island's tunnel couplings to the drain and source leads. Here we present results on SET device fabrication using focused electron beam induced deposition (FEBID) for island definition between pre-fabricated SET electrode structures. The island's nano-granular microstructure allows us, in conjunction with in situ tuning of the inter-grain tunnel coupling by post-growth electron irradiation, to study the effect of the island's electronic granularity on SET device performance. In addition we show that for reliable SET operation FEBID-associated co-deposit in proximity of the island has to be removed which can be accomplished by a novel in situ Ar ion etching process. For the low-temperature properties of functioning SET devices we obtain good agreement of capacitance values deduced from the current-voltage characteristics and capacitance calculations based on the geometry of the device electrodes and the microstructure of the island. Complementary simulations of the SET current-voltage characteristics based on the master equation approach are in good agreement with the experimental data. The observation of well-defined Coulomb oscillations indicates that FEBID-based SET structures can be useful as on-demand charge monitor devices with high lateral positioning flexibility.

We investigate in underdoped cuprates possible coexistence of the superconducting order at zero momentum and pair density wave (PDW) at momentum Q = (Π, Π) in the presence of a Néel order. By symmetry, the d-wave uniform singlet pairing dS ₀ can coexist with the d-wave triplet PDW dT _Q , and the p-wave singlet PDW p _Q can coexist with the p-wave uniform triplet pT ₀. At half filling, we find that the novel pS _Q + pT ₀ state is energetically more favorable than the dS ₀ + dT _Q state. At finite doping, however, the dS ₀ + dT _Q state is more favorable. In both types of states, the variational triplet parameters dT _Q and pT ₀ are of secondary significance. Our results point to a fully symmetric Z₂ quantum spin liquid with spinon Fermi surface in proximity to the Néel order at zero doping, which may not be adiabatically connected to the d-wave singlet superconductivity at finite doping with intertwining d-wave triplet PDW fluctuations and spin moment fluctuations. The results are obtained by variational quantum Monte Carlo simulations.

Single-layer superconductors are ideal materials for fabricating superconducting nano devices. However, up to date, very few single-layer elemental superconductors have been predicted and especially no one has been successfully synthesized yet. Here, using crystal structure search techniques and ab initio calculations, we predict that a single-layer planar carbon sheet with 4- and 8-membered rings called T-graphene is a new intrinsic elemental superconductor with superconducting critical temperature (Tc) up to around 20.8 K. More importantly, we propose a synthesis route to obtain such a single-layer T-graphene, that is, a T-graphene potassium intercalation compound (C4K with P4/mmm symmetry) is firstly synthesized at high pressure (>11.5 GPa) and then quenched to ambient condition; and finally, the single-layer T-graphene can be either exfoliated using the electrochemical method from the bulk C4K, or peeled off from bulk T-graphite C4, where C4 can be obtained from C4K by evaporating the K atoms. Interestingly, we find that the calculated Tc of C4K is about 30.4 K at 0 GPa, which sets a new record for layered carbon-based superconductors. The present findings add a new class of carbon-based superconductors. In particular, once the single-layer T-graphene is synthesized, it can pave the way for fabricating superconducting devices together with other 2D materials using the layer-by-layer growth techniques.

In this paper we give an overview of some recent progress in using holography to study various far-from-equilibrium condensed matter systems. Non-equilibrium problems are notoriously difficult to deal with, not to mention at strong coupling and when including quantum effects. Remarkably, using holographic duality one can describe and follow the real-time evolution of far-from-equilibrium systems, including those which are spatially inhomogeneous and anisotropic, by solving partial differential gravity equations. We sample developments in two broad classes of question which have recently been of much interest to the condensed matter community: non-equilibrium steady states, and quantum systems undergoing a global quench. Our discussion focuses on the main physical insights obtained from the gravity approaches, rather than comprehensive treatment of each topic or detailed descriptions of gravity calculations. The paper also includes an overview of current numerical techniques, as well as the holographic Schwinger-Keldysh approach to real-time correlation functions.

This review presents a survey of, and guide to, new materials physics (NMP) research. It begins with an overview of the goals of NMP and then presents important ideas and techniques for the design and growth of new materials. An emphasis is placed on the use of compositional phase diagrams to inform and motivate solution growth of single crystals. The second half of this review focuses on the vital process of generating actionable ideas for the growth and discovery of new materials and ground states. Motivations ranging from (1) wanting a specific compound, to (2) wanting a specific ground state to (3) wanting to explore for known and unknown unknowns, will be discussed and illustrated with abundant examples. The goal of this review is to inform, inspire, an even entertain, as many practitioners of this field as possible.

Complex metallic alloys belong to the vast family of intermetallic compounds and are hallmarked by extremely large unit cells and, in many cases, extensive crystallographic disorder. Early studies of complex intermetallics were focusing on the elucidation of their crystal structures and classification of the underlying building principles. More recently, ab initio computational analysis and detailed examination of the physical properties have become feasible and opened new perspectives for these materials. The present review paper provides a summary of the literature data on the reported compositions with exceptional structural complexity and their properties, and highlights the factors leading to the emergence of their crystal structures and the methods of characterization and systematization of these compounds.

Topological materials have become promising materials for next-generation devices by utilizing their exotic electronic states. Their exotic states caused by spin-orbital coupling usually locate on the surfaces or at the edges. Scanning tunneling spectroscopy (STS) is a powerful tool to reveal the local electronic structures of condensed matters. Therefore, STS provides us with an almost perfect method to access the exotic states of topological materials. In this topical review, we report the current investigations by several methods based on the STS technique for layered topological material from transition metal dichalcogenide Weyl semimetals (WTe₂ and MoTe₂) to two dimensional topological insulators (layered bismuth and silicene). The electronic characteristics of these layered topological materials are experimentally identified.

Although the 1T' phase is rare in the transition metal dichalcogenides (TMDCs) family, it has attracted rapid growing research interest due to the coexistence of superconductivity, unsaturated magneto-resistance, topological phases etc. Among them, the quantum spin Hall (QSH) state in monolayer 1T'-TMDCs is especially interesting because of its unique van der Waals crystal structure, bringing advantages in the fundamental research and application. For example, the van der Waals two-dimensional (2D) layer is vital in building novel functional vertical heterostructure. The monolayer 1T'-TMDCs has become one of the widely studied QSH insulator. In this review, we review the recent progress in fabrications of monolayer 1T'-TMDCs and evidence that establishes it as QSH insulator.

Recent studies in van der Waals coupled two-dimensional (2D) bilayer materials have demonstrated a new freedom for material engineering by the formation of moiré pattern. By tuning the twist angle between two layers, one can modulate their electronic band structures and therefore the associated electrical transport and optical properties, which are distinct from the original ones of each individual layer. These new properties excite great passion in the exploration of new quantum states and possible applications of 2D bilayers. In this article, we will mainly review the prevailing fabrication methods and emerging physical properties of twisted bilayer materials and lastly give out a perspective of this topic.